TOM NIGHTINGALE: Shaun Valentine was a talented player with the North Queensland Cowboys before he was forced to retire early a decade ago after multiple concussions.

But he says the shoulder charge ban is too far.

SHAUN VALENTINE: I mean, you're running directly at someone, you can see, most of the time, where it's coming from, and I do think there is a place for it.

I mean I got some great high shots and concussions, and I still believe there is a place for it in game.

TOM NIGHTINGALE: What do you think your concussions playing league were caused by?

SHAUN VALENTINE: Mine were all just high tackles and knocks to the head. I mean mine were bad shoulder charges I think, I got some shoulder charges that didn't affect me at all with concussions.

TOM NIGHTINGALE: He's now dealing with the effects of his sport concussions every day but he says the risk is part of the sport.

SHAUN VALENTINE: My son plays, and I've got no problem with that at all.

I don't have any problems with the way the game is, sorry, apart from refereeing, but as far as the physical side of it, there's not a lot you can do.

I mean, it is part of the game.

TOM NIGHTINGALE: Doctor Sam Sorrenti is a surgeon based in North Sydney, and represents the league's medical officers.

SAM SORRENTI: In some people it can cause serious irreversible damage. Not everyone has a predisposition for that, but at this stage, we have no ability of identifying those players which may have a predisposition.

Therefore it's much better to err on the side of being cautious rather than wait until we produce someone who could becomes a vegetable or someone who 15 years down the track has got memory loss when they could have avoided it if they haven't had any brain trauma.

TOM NIGHTINGALE: Is there any argument to go further than the shoulder charge ban and make other changes that would make the game safer?

SAM SORRENTI: At this stage, it's extremely difficult for the simple reason is that medicine is a constantly evolving discipline.

TOM NIGHTINGALE: Results have just been released from a four-year study of brains including those of former athletes and soldiers in the US.

They show every injured brain also involved a history of heavy trauma.

The results also show not everyone who was repeatedly concussed then developed an injury, and researchers are now studying why some are affected and not others.

Professor Caroline Finch is with Monash University's Australian Centre for Research into Injury in Sport and its Prevention. She says concussion effects could also be a major issue in local sport.

CAROLINE FINCH: The sorts of adverse outcomes you're talking about from concussion are things that manifest months, years after event, and we have no monitoring at all of injury outcomes in people long term.

TOM NIGHTINGALE: Do you think there should be that sort of monitoring, and if so, who would pay for it and how easy, logistically, would it be to set up?

CAROLINE FINCH: Look, we're getting more and more evidence that sports injuries are a major public health issue. They do lead to a large number of people attending hospitals.

We also know from some data in Victoria, most recently generated by my group, that the number of people who get admitted to hospitals for sports injury far exceeds the number of people who get admitted for road safety.

TOM NIGHTINGALE: The US study has been published in the journal 'Brain'.